Ports of Auckland's release of negotiation documents has sparked more threats from the Maritime Union.

Wharfies returned to work after several months of strikes in April, but a new collective agreement is still being negotiated.

The council-controlled port company and the union asked for help negotiating an agreement from the Employment Relations Authority, which appointed chief authority member Alastair Dumbleton as a "facilitator".

On Friday, PoA published a letter to workers from chief executive Tony Gibson and its collective bargaining proposal.

Mr Gibson says in the letter the company needs to shake up its rosters to fit the shipping schedule, while increasing pay rates by 10%, with a further performance bonus of up to 10%.

It will guarantee full-time workers 160 hours in a four-week roster cycle, with a minimum of 10 hours between shifts and the end of double-shifting.

He says without this flexibility the port will continue to lose work – such as Maersk's Southern Star service, which went to Tauranga last year.

"We can't wish our customers back, we have to win them back," Mr Gibson says in the letter.

"If we do nothing we'll lose more customers and end up a smaller port.

"Smaller ports need fewer staff."

On Saturday, the Maritime Union of New Zealand accused the Auckland Council-controlled company of breaching the law by publishing the documents.

Garry Parsloe, the union's national president, says it will be issuing proceedings about the "continued breach of good faith by this arrogant and heavy-handed company".

Mr Dumbleton issued a recommendation on Friday evening that none of the parties talk to the media until midday today, other than statements about the process of or progress in the so-called facilitation.

Ports of Auckland is owned by Auckland Council Investments Ltd, a council-controlled investment company.